Smart methane monitor

ABSTRACT

A method and apparatus for the detection of methane gas including a low-cost low-power infrared methane sensor integrated with a smart energy network endpoint node, a volume corrector, or an electronic data recorder for transmission of alarm conditions and detector data between the instrument and a remote gas utility company. An independent gas calibration/verification cell may be included in the methane detector for periodically testing the functioning and calibration of the infrared sensor. An infrared carbon monoxide sensor aid associated calibration/verification cell may also be installed with the methane sensor.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.12/758,627, filed Apr. 12, 2010, and allowed Jan. 8, 2015.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to remote monitoring systems, and inparticular to remote methane monitoring systems for the purpose ofdetecting the presence of natural gas leaks within residential,commercial, and industrial facilities.

2. Background Art

Natural gas utility companies operate approximately 61 million customergas meters in the United States alone, supplied by over one millionmiles of pipeline, 17 hundred transmission stations and 17 thousandcompressors. To help maintains security and integrity of this vastdistribution system, the natural gas utility industry installs volumecorrectors and electronic data recorders at compressor stations,metering stations, step-down stations and meter vaults, for example,which provide trend data about the functionality of the distributionsystem. A volume corrector is typically installed with a gas meter. Thevolume corrector accurately measures the pressure and temperature of thegas and corrects the volume flow estimation from the gas meter usingideal gas law calculations. Similarly, an electronic data recorderaccurately measures pressure and temperature and stores the information.Both types of installments communicate the stored results to the utilitycompany using proprietary supervisory control and data acquisition(SCADA) systems modulated over plain old telephone service (POTS).

Gas pipelines are also subject to regular inspections to detect leaks.Routine periodic leak surveys are costly, and it is estimated that thenatural gas distribution and transmission industry spends over $300million annually to survey the pipeline network for leaks. Moreover,because gas leaks may occur at appliances or within interiordistribution piping on the consumer side of the gas meter, utilitypipeline surveys are of limited effect.

Gas explosions due to leakage and accumulation of natural gas inend-user buildings are an unfortunate and too frequent occurrence.Currently, like smoke detectors, heat detectors, carbon monoxidedetectors and water sensors, there exists several types of discretenatural gas sensors that may be installed in homes or commercialbuildings that notify occupants when there is a predetermine minimumconcentration natural gas in the atmosphere. Such natural gas detectorsare typically stand-alone alarms that sound a warning when triggered sothat the occupants may safely evacuate. However, some models includerelay contacts so that they can be wired into a central alarm or homesecurity system. A security monitoring service may then notifyauthorities in the event an alarm is triggered.

Natural gas detectors may rely on varying detection methods andprinciples. For example, combustible gas indicators (CGIs) work on theprinciples of catalytic combustion and thermal conductivity of a gassample and thus sense virtually all combustible gases. CGIs arclow-sensitivity devices that are generally unable to detect gas mixturesmuch below the lower combustible concentration limit. A more sensitiveleak detector commonly used is the flame ionization detector (FID). TheFID operates on the principle of measuring the ionic concentrationproduced in a flame horning carbon compounds. Like the CGIs, FIDs sensehydrocarbon gases. While the CGI typically measures gas concentration inpercentage, the FID typically measures gas concentration in parts permillion (ppm). The CGI and FID both typically use an extractive sampleor measurement path. In this method, target gas concentration ismeasured by a detector installed in a measurement chamber through whichgases of interest are continually drawn from the immediate surroundingatmosphere.

The optical methane detector (OMD™) operates by absorption of infrared(IR) light by methane. Because natural gas primarily contains methanegas, detection of methane gas serves for detection of natural gas. It isa well known spectroscopic principle that gas molecules absorb energy innarrow bands (sometimes referred to as absorption lines) surroundingspecific wavelengths in the electromagnetic spectrum. For example,methane has strong absorption bands at 133 μm, 1.66 μm, 3.3 μm, and 7.6μm. At wavelengths falling even slightly outside the narrow absorptionband, there is essentially no absorption. Thus, an OMD measures theattenuation of an infrared light source passing through a gas sample atthe methane-characteristic absorption wavelength to determine thepresence of methane gas. An OMD is more selective than either a CGI or aFID, because it measures methane specifically and not all combustiblegases. OMDs generally use a short open path sample method, whicheliminates the sampling time delay associated with extractive samplingmethod of CGIs or FIDs. In a short open path configuration, the lightsource is transmitted across a line of sight and is either reflected toan optical detector by a fixed reflector of known characteristicslocated only a short distance from the light source or the light isreceived directly by a fixed detector located only a short distance awayfrom the light source. OMD sensitivity in detecting methane is of thesame order of magnitude as a FID.

A laser methane detector is a prior-art device that operates on the sameabsorption spectroscopy principle as an OMD but uses a rapidly andspecifically-tunable wavelength-modulated diode laser as a light source.By sweeping the laser wavelength between a non-absorption band and aparticular absorption band of a target gas molecule and monitoring thereflection measurements during the wavelength sweeps, both thebackground transmittance over the laser beam's path and theconcentration of target gas molecules integrated within the laser beam'spath can be accurately determined. A laser methane detector is thuswell-suited for utility company pipeline surveys, because a fixed samplechamber is not required and accurate measurements can be made over longand widely-varying path lengths.

However, CGIs, FIDs, OMDs, and laser detectors are generally consideredto be too expensive to be widely accepted for home use and thus findlimited use, typically in potentially hazardous industrial locations.Current sensors widely used in home natural gas detectors are based onelectrochemical catalytic semiconductors, whose electrical propertiesare altered in the presence of various hydrocarbon gases. These sensorsare inexpensive, but they have significant performance limitations.Electrochemical catalytic semiconductors are unstable, prone to drift,and subject to false alarms due to moisture or household chemicals. Thesensors, which are easily contaminated by household chemicals, have arelatively short life span. Additionally, there is no practical way forthe home owner to test the calibration and functioning of the detector.As a result, the homeowner is at risk that the methane sensor mayfrequently trigger false alarms or may not alarm at all when adetectable hazardous condition is present.

Although state and federal safety commissions are increasingly urgingthe use of natural gas monitors, there is currently little utilitycompany monitoring of detectable atmospheric gas levels at the end-userlocations. Low cost electrochemical semiconductor methane sensors aretoo prone to false alarms, and more reliable detectors have been tooexpensive to deploy. Perhaps a more significant barrier has been thelack of a low cost reliable infrastructure through which a multitude ofmethane detectors can communicate back to the utility company.

If reliable methane monitors are widely deployed at a gas utilitycompany's end-user locations and each monitor automatically notifies thegas utility company of actual pending dangers, proactive steps may betaken by the utility company to alleviate the danger before acatastrophe occurs.

3. Identification of Objects of the Invention

Therefore, a primary object of the invention is to provide acost-effective system and method for utility-provider-monitoring ofactual atmospheric gas levels at various distribution system andend-user locations, including residential, commercial and industrialbuildings.

Another object of the invention is to provide a methane detector thatuses Smart Energy™ communication networks for compatibility, rapiddeployment, and low cost.

Another object of the invention is to provide a method and apparatus formonitoring natural gas levels that provides the ability to monitor thegas level at a remote installation.

Another object of the invention is to provide a method and sensor formonitoring natural gas levels in which the functioning of the sensor canbe automatically or remotely tested and calibrated, and if not workingproperly, notification can automatically be provided to the end-user andto the gas company.

Another object of the invention is to provide a method and sensor formonitoring natural gas levels in which the results of sensor self-testsare further analyzed to project the need for service.

Another object of the invention is to provide a method and sensor formonitoring the atmosphere in remote locations in which carbon monoxidegas and natural gas levels may be present.

Another object of the invention is to provide a volume corrector withintegrated methane detector that communicates with a gas utilitycompany.

Another object of the invention is to provide an electronic datarecorder with integrated methane detector mat communicates with a gasutility company.

Another object of the invention is to provide a tire alarm withintegrated methane detector that communicates with a gas utilitycompany.

SUMMARY OF THE INVENTION

The objects described above and other advantages and features of theinvention are incorporated in a first embodiment in a method and systemfor the detection of methane gas including a low-cost low-power infraredmethane sensor integrated with a smart energy network endpoint node fordata transmission between die instrument and a remote gas-utilitycompany.

In a second embodiment of the invention, a low-cost low-power infraredmethane sensor is integrated with a volume corrector or an electronicdata recorder.

An independent gas calibration ceil may be included in the methanedetector for periodically testing the functionality and calibration ofthe infrared sensor. An infrared carbon monoxide sensor may also beinstalled with the methane sensor.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is described in detail hereinafter on the basis of theembodiments represented in the accompanying figures, in which;

FIG. 1 is a functional schematic diagram of a smart methane monitoringsystem according to a first embodiment of the invention that isintegrated with a wireless smart energy network, which is in turn linkedto a hardwired local area network for communicating with a gas utilitycompany via the internet;

FIG. 2 is a functional schematic diagram of the smart methane monitoringsystem of FIG. 1 showing an alternate interface linking the wirelesssmart energy network to the hardwired local area network;

FIG. 3 is a functional schematic diagram of a smart methane monitoringsystem according to a second embodiment of the invention that isintegrated with a wireless smart energy network linked to a wirelesslocal area network for communicating with a gas utility company via theinternet;

FIG. 4 is a functional schematic diagram of a smart methane monitoringsystem according to a third embodiment of the invention showing amethane detector included as a device within a local area computernetwork for communicating with a gas utility company via the internet;

FIG. 5 is a perspective view in partial cross-section of a smart home ofa subscriber to a natural gas provider according to a preferredembodiment of the invention showing a smart energy home area networkimplemented according to the embodiment of FIG. 2, including a smartenergy-enabled gas meter, a status indicator, and a smart methanedetector; and

FIG. 6 is a schematic diagram of a remote volume corrector or anelectronic data recorder integrated with a methane detector according toa fourth embodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT OF THE INVENTION

FIGS. 1-3 illustrate exemplar “Smart Energy™” or “Smart Grid” networks10 according to a preferred embodiment of the invention. “Smart Energy”is a relatively new and rapidly developing technology being embraced bya number of utility companies. Smart energy offers utility companiessecure, easy-to-use wireless home area networks (HAH) for implementingenergy management programs under anticipated government mandates tocontrol or ration the distribution of energy. Smart energy allowsutilities to directly communicate with smart meters, thermostats, loadcontrol devices, and other-smart appliances of end users. Advancedmetering is available for multiple energy commodities includingelectricity, natural gas and water. Advanced metering, which allowsmultiple measurement types such load profile, power factor, summation,demand and tiers, can provide real-lime consumption information to boththe consumer and the utility. Demand response and load control is asmart energy technique for scheduling disconnection, reconnection and/oradjustment of multiple specific groups of devices including furnaces,heat pumps, air conditioning units, water heaters, and lighting. Forexample, during peak demand periods utilities can automatically adjustset points on programmable communicating thermostats or can turn offlarge appliances such as air conditioning units, swimming pool pumps,ovens, ranges, and resistance heaters.

Smart energy network 10 includes a wireless network 11 over whichvarious locally distributed smart-energy-compliant sensors and devicescommunicate. Wireless network 11 ideally complies with IEEE 802.15.4wireless and ZigBee™ communication protocol specifications using theSmart Energy™ profile. IEEE 802.15.4 wireless specification calls foroperation in the unlicensed industrial, scientific and medical (ISM)radio bands—915 MHz in the USA and Australia, 868 MHz in Europe, and 2.4GHz in most other locations worldwide. Binary phase shift keying (BPSK)modulation is used in the 915 and 868 MHz bands, and orthogonalquadrature phase shift keying (QPSK) is used in the 2.4 GHz band toachieve an uncorrected data rate of 40 kbit/s per channel in the 915 MHzband, 20 kbit's in the 868 MHz band, and 250 kbit's per channel in the2.4 GHz band, respectively. Transmission range extends up to between 125and 250 feet.

ZigBee is a specification for a suite of high level communicationprotocols for use with small, low-power digital radios to form wirelesspersonal area networks (WPANs) or home area networks (HANs). ZigBee issuitable for low-power low-bandwidth applications. Because ZigBee is anopen standard, it supports a competitive marketplace of multiplevendors, which lowers cost. ZigBee certified devices ensureinteroperability, and its robust ability for automatic networkregistration, using either pre-installed cryptographic keys or standardpublic keys, provides a flexible secure network that is simple to use.In addition to home and industrial automation and control, ZigBee iswidely used for smart energy technology.

ZigBee radio transceiver chips are commercially available withintegrated microcontrollers, typically up to 256 kBytes of flash memory,and a prepackaged ZigBee software stack. The ZigBee protocol enables ageneral-purpose, self-organizing ad hoc mesh network of nodes thatcommunicate using a “carrier sense, multiple access/collision avoidance”scheme. Simply put, the nodes communicate within the network in the samemanner that polite people converse—before transmitting, each nodebriefly “listens” to the network to ensure no other node is activelytransmitting.

The base of wireless network 11 is a ZigBee network coordinator 20.Coordinator 20 creates and manages wireless network 11, storinginformation about each node in the network including security keys. FIG.1 shows three ZigBee end devices 30, 31, 32 forming the other nodes ofwireless network 11, although a greater or lesser number of devices mayactually be present in any particular network 11. A ZigBee end deviceneed contain just enough functionality to communicate with coordinator20 and need not relay data from other end devices. This simplicityreduces production costs and allows an end device 30, 31, 32 to remainin a low-power dormant mode a significant amount of time, thus enhancingbattery life.

ZigBee end device 30 is a methane detector that is integrated withZigBee interface electronics and implements the Smart Energy™ profile.Methane detector 30 is powered from a standard household power outletand has a battery backup, although other power configurations may beused. Methane detector 30 is preferably able to detect a level ofmethane of about 500 ppm, notify the building occupants of an alarmcondition and concurrently notify the gas utility company via the smartenergy network 10. In a preferred embodiment, methane detector 30 usesan infrared sensor that operates on well-known spectroscopy principles.By using IR sensors, high selectivity, stability, long-life and lowfalse-alarm-rate methane detectors 30 are obtained. More preferablystill, methane detector 30 uses non-dispersive infrared (NDIR) sensors,although laser-based, opto-acoustic, LED, or fiber optic sensors mayalso be used as appropriate.

A NDIR methane sensor includes an IR source, a transparent samplechamber, an optical filter, and an IR detector. All wavelengths producedby the IR source are directed through the sample chamber toward the IRdetector. The optical filter, which eliminates all light except for oneor more of the characteristic absorption wavelengths of methane gasand/or carbon monoxide, is placed directly in front of the IR detector.Recent advancements in IR detectors and sources have enabled thedevelopment of lower cost NDIR sensors. As IR sensors are understood byroutineers in the art, the topic is not discussed further herein.

In a preferred embodiment, a independent calibration gas cell isincluded in detector 30 and is used to test the functionality,calibration and alarm verification of the infrared sensor. Ahermetically sealed glass vile is temporarily placed within the lightpath of the sensor. This calibration cell contains a known concentrationof methane gas and/or carbon monoxide. Calibration readings areperiodically taken. For example, detector 30 automatically performsroutine self-tests. Detector 30 may also be remotely commanded vianetwork 10 to perform a self-test. The results of thecalibration/verification checks are compared to internally storedpresets. If detector 30 is not working properly, notification isprovided to the homeowner and/or to the gas utility company. Self-testresults may also be transmitted to the gas utility company for furtheranalysis to project the need for detector service. In another embodimentusing a laser based IR sensor, a self test and calibration may alsoinclude measurement and adjustment of a laser's wave length.

An optional infrared-based carbon monoxide sensor may also installedwith-the methane detector 30 for detection of both carbon monoxide andnatural gas. In this configuration, a dedicated carbon monoxidecalibration/verification cell may be included, or a singlecalibration/verification cell that includes known concentrations of bothcarbon monoxide gas and methane may be used.

ZigBee end device 31 is a display unit that is integrated with ZigBeeinterface electronics. Display 31 is programmed to display the methanegas concentration detected by methane detector 30. Display 31 mayindicate gas concentration in ppm or percent of lower explosive limit,for example.

ZigBee end device 32 is shown as a generic utility meter, such as anelectricity, gas or water meter, which forms no part of the presentinvention but is illustrated as being a node in a typical smart energynetwork 10.

Coordinator 20 bridges the ZigBee wireless network 11 with a standardcomputer network 12, which is typically a IEEE 802.3 hardwired Ethernetlocal area network (LAN) as shown in FIGS. 1 and 2 or a wireless IEEE802.11 WiFi wireless local area network (WLAN) as shown in FIG. 3.

In FIG. 1, coordinator 20 employs a Texas Instruments® CC2530 orequivalent ZigBee radio chip. The TI CC2530 offers dual universalsynchronous/asynchronous receiver/transmitter (USART) interfaces. Forthis reason, coordinator 20 of FIG. 1 employs a serial computerinterface 21, such as a ES-232, RS-422, RS-485, IrDA, or USB interface.An Ethernet-to-serial converter 40, such as one commercially availablefrom Lantronix® or NetBurner,® links coordinator 20 to LAN 12. In FIG.2, coordinator 20 includes onboard circuitry to provide an Ethernetinterface, such as a 10-Base-T interface, and is thus connected directlyto LAN 12. In FIG. 3, coordinator 20 includes onboard circuitry toprovide WiFi connectivity for bridging to WLAN 12.

Computer network 12 may include an optional computer 50. Computer 50includes a webpage postal or similar software by which an operator or ahomeowner, for example, may view the status of smart energy network 10,including the real-time status of smart methane monitor 30. The webpageportal may include password protection.

Computer network 12 includes an internet gateway 60 such as a cable ordigital subscriber line (DSL) modem. Internet gateway preferablyincludes router functionality for multiple network connections. Ascomputer and internet networking are well known in the art, the topic isnot discussed in further detail herein.

Although FIGS. 1-3 each illustrate only one local smart energy network10, a large number of individual local smart energy networks 10 arecontemplated—ideally one for each building served by a gas utilitycompany. The gas utility company provides one or more server computersystems 80 that are connected to the internet 70 for monitoring thelarge number of customer smart energy networks 10. When a smart methanedetector 30 in one of the smart energy networks 10 generates ahigh-methane-level alarm, the detector 30 transmits that alarm status toutility server 80. Upon receiving the alarm, the gas utility company canthen respond by dispatching service technicians to shut off the electricand gas service and notify local fire departments, etc. Smart methanedetector 30 may also be programmed to contact the customer calls in analarm condition, such as by telephone calls to POTS lines, cell phones,SMS text messaging, email, Twitter™, Facebook™, MySpace™, or aSmartphone™ application.

FIG. 1 illustrates a first method for back-up communications using aPOTS modem 90 should the broadband internet connection 71, gateway 60,or network 12 fail. In the event of an alarm condition, coordinator 20establishes a dial-up connection 22 directly with utility company server80. Preferably server 80 includes a number of POTS modems and incomingdial-up lines for supporting a number of emergency dial-up calls at atime. Modem 90 may be internal to or external from coordinator 20.

FIG. 2 illustrates a second method for back-up communications using aPOTS modem 90 should the broadband internet connection 71 fail. Gateway60 is configured to automatically establish a dial-up connection 72 toan internet service provider using modem 90 whenever it detects afailure of broadband connection 71. In this manner, the back-up internetconnection is transparent to the ZigBee coordinator 40 and wirelessnetwork 11. Modem 90 may be internal to or external from gateway 60.

Although the preferred embodiment of the invention is described asemploying a ZigBee-compliant wireless network 12, WiFi, Bluetooth orother types of wireless networks 12 may also be used between methanedetector 30 and internet 70 as appropriate. For example, FIG. 4illustrates an alternate embodiment of a smart energy network 10′ inwhich methane detector 30′ and display 31′ communicate using an IEEE802.11 wireless WiFi standard. As such, methane detector 30′ and display31′ are linked directly with gateway/router 60.

FIG. 5 depicts how the smart energy network 10 of FIG. 2 might beimplemented within a typical house 100. Smart methane detectors 30 arelocated near gas appliances. For example, a first methane detector 30Afor a carbon monoxide detector, for example) is located in the basementadjacent to a gas furnace 102 and water heater 104, and a second methanedetector 30B is located in the kitchen near a gas range 106. Additionalmethane detectors and/or carbon monoxide detectors (not shown) may belocated in a laundry room, utility room, attic, or garage, for example.Coordinator 20, computer 50 and gateway/router 60 are located in a homeoffice, although a bedroom, library, study, conservatory, home theatreor any other convenient location may be used, provided coordinator 20 islocated within wireless range of all of the smart energy end devices.Display unit 31 is placed in a prominent location in the kitchen,although it or additional display units may be located near a thermostat120, an alarm panel, intercom station, or other annunciator device. Asmart energy enabled thermostat 120 and smart energy gas meter 130 areshown.

FIG. 6 illustrates a methane detector system according to anotherembodiment of the invention in which a low power methane detector 230 isintegrated into a flow corrector or electronic data recorder 200 for usein metering stations, step-down stations and similar remote locationswithin a natural gas distribution system. Volume corrector or electronicdata recorder 200 includes one or more pressure transducers 202 and atemperature probe 204, the signals from which are conditioned by analogcircuitry 206, sampled by an analog-to-digital converter (ADC) 208, andstored as digital data in memory 210. Digital pulses from a gas meter212 are also collected. A microcontroller or microprocessor 214coordinates the collection and transmission of data and may performvolume correction calculations. A POTS modem 290 is connected to volumecorrector or electronic data recorder 200 for interfacing the device tothe SCADA system of a gas utility company, although other datatransmission methods may be used including a broadband internet gateway,frame relay service, cellular telephone, text, or G3 internet service,or other radio communication. Volume corrector or data recorder 200typically includes a display 216 and a battery 218.

Like methane detector 30, 30′ of FIGS. 1-5, methane detector 230 ispreferably an IR OMD such as an NDIR detector. Detector 230 includes anIR light source 231 (which may be a laser or LED), a sample chamber 232,and an IR detector 233. In the case of a non-monochromatic light source231, detector 230 also includes one or more optical filters 234. Anoptional calibration cell 236 may be included, which may be selectivelypositioned into the detection optical path in place of sample chamber232. Detector 230 interlaces to ADC 208 via analog signal conditioningcircuitry 238. Processor 214 is programmed to record methane levels, totransmit high-methane-level alarms to the gas utility company, and tocontrol which gas cell—sample chamber 232 or calibration cell 236—ispositioned in the measurement optical light path. Detector 230 may alsoinclude a carbon monoxide detector as discussed above with respect tomethane detector 30.

The Abstract of the disclosure is written solely for providing theUnited States Patent and Trademark Office and the public at large with away by which to determine quickly from a cursory reading the nature andgist of the technical disclosure, and it represents solely a preferredembodiment and is not indicative of the nature of the invention as awhole.

While some embodiments of the invention have been illustrated in detail,the invention is not limited to the embodiments shown; modifications andadaptations of the above embodiment may occur to those skilled in theart. Such modifications and adaptations are in the spirit and scope ofthe invention as set forth herein:

What is claimed is:
 1. A natural gas distribution system comprising gasutility apparatus of a gas utility company which supplies natural gas toa plurality of consumer locations via a natural gas distribution system,said apparatus including a service computer system (80) which isconnected to a communications network, a plurality of methane detectors(30) disposed so that each of said plurality of consumer locations hasat least one of said plurality of methane detectors, each of saidplurality of methane detectors having a low-power, low-bandwidth radiotransceiver, an infrared light source (231), an infrared light detector(233) disposed so as to receive light from said infrared light source,and a sampling chamber (232) disposed between said infrared light sourceand said infrared Sight detector, smart energy communication networks(10) that link each of said plurality of methane detectors (30) withsaid communications network for communication with said service computersystem (80) of said gas utility company, said smart energy communicationnetworks (10) each including a network coordinator (20) in communicationwith said internet (70) for communication with said service computersystem (SO) of said gas utility company, said plurality of networkcoordinators (20) placed at one of said consumer locations so that eachof said plurality of methane detectors (30) is in wireless communicationwith at least one of said plurality of network coordinator (20),circuitry disposed in each of said methane detectors (30) which isarranged and designed to notify said service computer system (80) ofsaid gas utility company of high methane gas conditions via said smartenergy communication network (10), and a display device (31) disposed inone of said consumer locations, said device (31) being in wirelesscommunication with one of said plurality of network coordinators (20)via said smart energy wireless network (11), said display devicedesigned for displaying said methane gas conditions detected by said atleast one of said plurality of methane detectors.